Hypertension and alterations in central catecholamines after preoptic recess lesions

Catecholamine concentrations were measured in brain regions of rats with lesions of the anteroventral third ventricle (AV3V-X rats) or parietal cortex (CORT-X) and of control-operated (CONT) rats. Three hours after surgery, total norepinephrine (NE) concentrations in all brain regions measured of AV3V-X rats were less than those of CONT or CORT-X rats. Epinephrine (EPI) concentrations were decreased in the medulla and hypothalamus, but dopamine levels were unchanged. Also, extracellular NE concentration, estimated by in vivo microdialysis techniques, was increased in the anterior hypothalamic nucleus (AHNE) and dorsomedial medulla (DMMNE) of AV3V-X rats compared with CONT rats. Increased DMMNE paralleled blood pressure increases. DMMNE did not change after blood pressure was increased by intravenous angiotensin II infusion (60 ng/min) in CONT rats. Thus 1) AV3V lesions result in decreased NE and EPI concentrations in multiple brain regions; 2) acute reductions in central NE in AV3V-X rats are associated with increased extracellular NE in the AH and DMM, suggesting increased NE release; and 3) although increased DMMNE is temporally related to increased blood pressure following AV3V lesions, increased DMMNE is not a response to the hypertension per se.